Vehicle clutches of the diaphragm spring type typically include a flywheel connected to a driving shaft from the vehicle engine, a clutch disc splined onto a driven shaft leading to the vehicle transmission, an axially movable annular pressure plate rotatable with the flywheel and having a fulcrum surface on the plate surface opposite to the clutch disc, a clutch cover secured to the flywheel, a diaphragm or Belleville spring engaging the fulcrum surface of the pressure plate and a separate fulcrum on the cover, and a release bearing axially reciprocable on the driven shaft when actuated by the vehicle operator to engage radially inwardly extending fingers of the diaphragm spring. During actuation of the diaphragm spring by the release bearing to advance or retract the pressure plate, the spring pivots about wire pivot rings mounted on the clutch cover with the peripheral portion of the spring engaging the fulcrum surface of the pressure plate. Upon release and re-engagement of the clutch assembly, all of the parts will resume the same relationship.
As wear occurs to the clutch friction facings, the pressure plate moves a greater distance toward the flywheel to engage the clutch disc, with the result that the diaphragm spring moves through a greater arc of travel for complete clutch engagement. This change in pressure plate position reduces the clearance between the spring fingers and the release bearing and the free travel at the clutch pedal. If the car is not serviced in time and the free travel reestablished, the fingers may ride the bearing causing clutch slippage. To alleviate this problem, the vehicle operator must have the clutch serviced to reposition the release bearing. A large percentage of clutch failures in passenger cars have been due to neglect in maintaining proper adjustment of the clutch system.
To overcome this problem, various methods of automatic adjustment were attempted either through adjustment of the release bearing carrier or by adjusting the fulcrum surface of the pressure plate. The present invention relates to an improved adjustment device obviating previously known problems.